Intermediate filaments (IF) are a class of proteins which are part of a large family of cytoskeletal proteins. Within the class there exist five components which differ according to the embryological origin of the cell in which they are found. Vimentin are found in cells of mesodermal or neuroectodermal origin, cytokeratins are found in cells of epithelial origin, desmin are found in smooth and striated muscle cells, glial fibrillary acidis protein (GFAP) are found in cells of glial origin and neurofliments are found in neuroectodermal cells, nerve cells and neurons. (Kurki and Virtanan, J. Imm. Methods 67:209-223 (1984); Moll, R., et al. Cell. 31:11-24 (1982); Lazarides, et al. Ann. Rev. Biochem. 51:219-250 (1982); Osborn, M., Cell. 31:303-306 (1982)). Other intermediate filaments have been described but they tend to be either congeners or conjugates of the above five main groups. Means have been sought for rapid and simple identification and measurement of IF in tissue specimen. It is of importance in research on the fundamental biochemistry of cells to be able to observe IF in various kinds of cells. Moreover, in the case of cancerous tissues, especially tumors, it is important to known the embryological origin of the cells in the tumor in order to make a better diagnosis and treatment of the tumor. Metastatic deposit of cells can be of several possible sources--breast, lymph node or brain for example--which may be distinguished by embryological origin and hence kind of IF. By measuring IF in an excised tissue specimen, the source of the tumor may be identified. Treatment may be designed accordingly.
Monoclonal antibodies are highly specific, sensitive reagents for identifying proteins. Knowledge about the surface antigenic structure of several types of human cancers has advanced rapidly with mouse monoclonal antibodies as serological probes, and application of these reagents to cancer diagnosis and therapy is underway. Production of human monoclonal antibodies, however, has proved more difficult to achieve. Despite much effort by many laboratories around the world, there are relatively few reports of success in the literature.
Human monoclonal antibodies which recognize cell surface and intracellular antigens derived from lymphocytes of patients with malignant myeloma have been reported (Houghton, et al, J. Exp. Med. July, 1983). Human monoclonal antibodies recognizing other cellular antigens have been made from lymphocytes of normal individuals or individuals having renal cancer, lung cancer, breast cancer or lymphoproliferative disease. (Cote, et al. Pro. Nat'l. Acad. Sci. April, 1983). Other human monoclonal antibodies capable of detecting intracellular components such as IF have been sought.